Climate engineering

Climate engineering (or geoengineering) is an umbrella term for both carbon dioxide removal and solar radiation modification, when applied at a planetary scale.^[1]^: 6–11 However, these two processes have very different characteristics. For this reason, the Intergovernmental Panel on Climate Change no longer uses this overarching term.^[1]^: 6–11^[2] Carbon dioxide removal approaches are part of climate change mitigation. Solar radiation modification is reflecting some sunlight (solar radiation) back to space.^[3] All forms of climate engineering cannot be standalone solutions to climate change, but need to be coupled with other forms of climate change mitigation.^[4] Some publications place passive radiative cooling into the climate engineering category. This technology increases the Earth's thermal emittance.^[5]^[6]^[7] The media tends to use climate engineering also for other technologies such as glacier stabilization, ocean liming, and iron fertilization of oceans. The latter would modify carbon sequestration processes that take place in oceans.

Some types of climate engineering are highly controversial due to the large uncertainties around effectiveness, side effects and unforeseen consequences.^[8] However, the risks of such interventions must be seen in the context of the trajectory of climate change without them.^[9]^[10]

According to climate economist Gernot Wagner the term geoengineering is "largely an artefact and a result of the terms frequent use in popular discourse" and "so vague and all-encompassing as to have lost much meaning".^[8]^: 14

^ ^a ^b IPCC (2022) Chapter 1: Introduction and Framing in Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA
^ IPCC, 2021: Annex VII: Glossary [Matthews, J.B.R., V. Möller, R. van Diemen, J.S. Fuglestvedt, V. Masson-Delmotte, C. Méndez, S. Semenov, A. Reisinger (eds.)]. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 2215–2256, doi:10.1017/9781009157896.022.
^ National Academies of Sciences, Engineering (2021-03-25). Reflecting Sunlight: Recommendations for Solar Geoengineering Research and Research Governance. doi:10.17226/25762. ISBN 978-0-309-67605-2. S2CID 234327299. Archived from the original on 2021-04-17. Retrieved 2021-04-17.
^ Munday, Jeremy (2019). "Tackling Climate Change through Radiative Cooling". Joule. 3 (9): 2057–2060. doi:10.1016/j.joule.2019.07.010. S2CID 201590290. Further, radiative cooling cannot be a complete, standalone solution, but rather is part of a more comprehensive approach that must include CO2 reduction. Otherwise, the radiative balance will not last long, and the potential financial benefits of mitigation will not fully be realized because of continued ocean acidification, air pollution, and redistribution of biomass.
^ Zevenhovena, Ron; Fält, Martin (June 2018). "Radiative cooling through the atmospheric window: A third, less intrusive geoengineering approach". Energy. 152 – via Elsevier Science Direct. An alternative, third geoengineering approach would be enhanced cooling by thermal radiation from the Earth's surface into space.
^ Wang, Tong; Wu, Yi; Shi, Lan; Hu, Xinhua; Chen, Min; Wu, Limin (2021). "A structural polymer for highly efficient all-day passive radiative cooling". Nature Communications. 12 (365): 365. doi:10.1038/s41467-020-20646-7. PMC 7809060. PMID 33446648. One possibly alternative approach is passive radiative cooling—a sky-facing surface on the Earth spontaneously cools by radiating heat to the ultracold outer space through the atmosphere's longwave infrared (LWIR) transparency window (λ ~ 8–13 μm).
^ Chen, Meijie; Pang, Dan; Chen, Xingyu; Yan, Hongjie; Yang, Yuan (2022). "Passive daytime radiative cooling: Fundamentals, material designs, and applications". EcoMat. 4. doi:10.1002/eom2.12153. S2CID 240331557. Passive daytime radiative cooling dissipates terrestrial heat to the extremely cold outer space without using any energy input or producing pollution. It has the potential to simultaneously alleviate the two major problems of energy crisis and global warming.
^ ^a ^b Gernot Wagner (2021). Geoengineering: the Gamble.
^ Matthias Honegger; Axel Michaelowa; Sonja Butzengeiger-Geyer (2012). Climate Engineering – Avoiding Pandora's Box through Research and Governance (PDF). FNI Climate Policy Perspectives. Fridtjof Nansen Institute (FNI), Perspectives. Archived from the original (PDF) on 2015-09-06. Retrieved 2018-10-09.
^ Zahra Hirji (October 6, 2016). "Removing CO2 From the Air Only Hope for Fixing Climate Change, New Study Says; Without 'negative emissions' to help return atmospheric CO₂ to 350 ppm, future generations could face costs that 'may become too heavy to bear,' paper says". insideclimatenews.org. InsideClimate News. Archived from the original on November 17, 2019. Retrieved October 7, 2016.

[AR6_WGIII_Ch_1-1] IPCC (2022) Chapter 1: Introduction and Framing in Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA

[IPCC_AR6_WGI_Glossary-2] IPCC, 2021: Annex VII: Glossary [Matthews, J.B.R., V. Möller, R. van Diemen, J.S. Fuglestvedt, V. Masson-Delmotte, C. Méndez, S. Semenov, A. Reisinger (eds.)]. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 2215–2256, doi:10.1017/9781009157896.022.

[:022-3] National Academies of Sciences, Engineering (2021-03-25). Reflecting Sunlight: Recommendations for Solar Geoengineering Research and Research Governance. doi:10.17226/25762. ISBN 978-0-309-67605-2. S2CID 234327299. Archived from the original on 2021-04-17. Retrieved 2021-04-17.

[:023-4] Munday, Jeremy (2019). "Tackling Climate Change through Radiative Cooling". Joule. 3 (9): 2057–2060. doi:10.1016/j.joule.2019.07.010. S2CID 201590290. Further, radiative cooling cannot be a complete, standalone solution, but rather is part of a more comprehensive approach that must include CO2 reduction. Otherwise, the radiative balance will not last long, and the potential financial benefits of mitigation will not fully be realized because of continued ocean acidification, air pollution, and redistribution of biomass.

[:442-5] Zevenhovena, Ron; Fält, Martin (June 2018). "Radiative cooling through the atmospheric window: A third, less intrusive geoengineering approach". Energy. 152 – via Elsevier Science Direct. An alternative, third geoengineering approach would be enhanced cooling by thermal radiation from the Earth's surface into space.

[:122222-6] Wang, Tong; Wu, Yi; Shi, Lan; Hu, Xinhua; Chen, Min; Wu, Limin (2021). "A structural polymer for highly efficient all-day passive radiative cooling". Nature Communications. 12 (365): 365. doi:10.1038/s41467-020-20646-7. PMC 7809060. PMID 33446648. One possibly alternative approach is passive radiative cooling—a sky-facing surface on the Earth spontaneously cools by radiating heat to the ultracold outer space through the atmosphere's longwave infrared (LWIR) transparency window (λ ~ 8–13 μm).

[:52-7] Chen, Meijie; Pang, Dan; Chen, Xingyu; Yan, Hongjie; Yang, Yuan (2022). "Passive daytime radiative cooling: Fundamentals, material designs, and applications". EcoMat. 4. doi:10.1002/eom2.12153. S2CID 240331557. Passive daytime radiative cooling dissipates terrestrial heat to the extremely cold outer space without using any energy input or producing pollution. It has the potential to simultaneously alleviate the two major problems of energy crisis and global warming.

[:04-8] Gernot Wagner (2021). Geoengineering: the Gamble.

[perspectives2-9] Matthias Honegger; Axel Michaelowa; Sonja Butzengeiger-Geyer (2012). Climate Engineering – Avoiding Pandora's Box through Research and Governance (PDF). FNI Climate Policy Perspectives. Fridtjof Nansen Institute (FNI), Perspectives. Archived from the original (PDF) on 2015-09-06. Retrieved 2018-10-09.

[10] Zahra Hirji (October 6, 2016). "Removing CO2 From the Air Only Hope for Fixing Climate Change, New Study Says; Without 'negative emissions' to help return atmospheric CO₂ to 350 ppm, future generations could face costs that 'may become too heavy to bear,' paper says". insideclimatenews.org. InsideClimate News. Archived from the original on November 17, 2019. Retrieved October 7, 2016.

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